The production of allergic eczematous contact deratitis (AECD) in humans due to exposure to dermatotoxic plant constituents poses a major clinical problem to dermatologists and immunologists. Recent published findings in our laboratory have established the structure identification and dermatotoxicity of numerous naturally-occurring chemicals that are present in native, agricultural and ornamental plants that pose occupational hazards. In some cases, we have established that the secondary constituents are more potent sensitizers than the "urushiols" of Toxicodendron. In this project, we propose to expand our experimental chemodermatological investigations to include numerous important economical plants, such as guayule (Parthenium argentatum), English Ivy (Hedera), the desert scorpion flower (Phacelia) and members of the sunflower (Asteraceae) family. We specifically propose to (i) elucidate the major contact allergens utilizing guinea pigs for our bioassays and maximization tests, (ii) determine the degree of cross-sensitization of structurally related compounds and (iii) develop in vitro and in vivo methods for elucidating their production, mode of antigen (skin or serum proteins) formation and the site(s) on cell membranes where the allergens are complexing. An understanding of the biotransformation and activation of contact allergens will lead to a greater understanding of skin inflammation states and immune responses to antigens. Also, the chemical investigation of important landscape plants, like English ivy, which is grown around elementary school district playgrounds, will permit us to understand the chemistry of the contact allergens, the degree of dermatitis among children and suggest the proper hyposensitization.